1. Field of the Invention
This invention relates to an abrasive tape to be used for polishing or cleaning of a magnetic head for a magnetic recording and reproducing apparatus or to be used for polishing, burnishing, texturing, or cleaning of various materials, particularly magnetic recording media. This invention particularly relates to an abrasive tape to be used for rough polishing, finish polishing, or cleaning of a magnetic head for video tape recorders or audio decks.
2. Description of the Prior Art
Video or audio magnetic heads are required to have very smooth tape sliding surfaces and to be free of any foreign substance, such as dust. Therefore, in general, during the process for making the magnetic head, the magnetic head is located at a predetermined position after being roughly polished, and two reels are located with the magnetic head intervening therebetween. In this state, an abrasive tape is moved between the two reels in order to polish the tape sliding surface of the magnetic head. Also, an abrasive tape is incorporated in a cassette and moved therein in order to remove any foreign substance from the tape sliding surface of the magnetic head. In general, the abrasive tape comprises a flexible substrate and a coating layer, which is overlaid on the flexible substrate and primarily contains fine abrasive grains and a binder. It is important for the abrasive tape to be provided with the flexible substrate and to be thereby capable of accurately polishing and smoothing the tape sliding surface of the magnetic head and reliably removing any foreign substance from the tape sliding surface of the magnetic head such that a magnetic tape can snugly fit to and move along the curved surface of the tape sliding surface of the magnetic head.
With the rapid advances made in magnetic tapes capable of recording magnetic information at a high density in recent years, various types of magnetic heads corresponding to the magnetic tapes have heretofore been proposed. Specifically, various magnetic heads, such as thin-film heads, amorphous heads, laminated heads, MIG heads, and MR heads, have been proposed through improvements in the magnetic material and the shape of the magnetic head and have widely been used in practice for high-density recording systems, such as S-VHS system and 8 mm video systems. Also, it has become more important than before that a magnetic head having a small width can be polished to a desired shape and to a smooth finish without being deteriorated, and that foreign substances clinging to a magnetic head can be removed from the magnetic head without the effective depth being decreased.
Further, with the rapid advances made in magnetic recording media capable of recording magnetic information at a high density in recent years, there has arisen a tendency in the magnetic recording medium industry, and the like, toward increased use of thinner magnetic recording media. However, with conventional thin cleaning tapes, a sufficient depth of polishing of the magnetic recording medium cannot be obtained. Moreover, with conventional abrasive tapes, magnetic heads cannot be polished to a shape suitable for thin magnetic tapes.
Furthermore, during the process for polishing a magnetic head, problems have heretofore been encountered in that the magnetic head is deteriorated. This is presumably because, when an abrasive tape slides on and polishes the surface of the magnetic head, heat is generated at the boundary between the surface of the magnetic head and the abrasive tape, and mechanical force is locally applied to the surface of the magnetic head. In particular, in cases where a magnetic head suitable for the recording of magnetic information at a high density is polished, deterioration of the surface of the magnetic head causes the output power of the magnetic recording and reproducing system to decrease markedly.
As a thin abrasive material, an abrasive sheet, which comprises an aromatic polyimide and abrasive grains kneaded therein and has a thickness falling within the range of 5 .mu.m to 200 .mu.m, has been proposed in Japanese Patent Publication No. 4(1992)-40156. However, the proposed abrasive material cannot come into close and uniform contact with a magnetic head and causes uneven wear to occur on the magnetic head. Also, in cases where the proposed abrasive material is used to polish a magnetic head for the recording of magnetic information at a high density, the proposed abrasive material inevitably causes the surface of the magnetic head to deteriorate.
In Japanese Unexamined Patent Publication No. 2(1990)-292179, an abrasive tape is proposed which employs a polyamide resin having a Young's modulus of nor lower than 600 kg/mm.sup.2 as a substrate. However, the proposed abrasive tape cannot completely eliminate the problems described above.